Most modern rifles today are shoulder-mounted, magazine-fed and fire centerfire cartridges. Such rifles may be fully automatic (i.e., fire continuously as long as the trigger is depressed), semi-automatic (i.e., fire only one round per each trigger pull) or bolt action (i.e., require manual reload after each round is fired). While fully automatic and bolt action rifles are primarily employed for combat and hunting applications, respectively, semi-automatic rifles are regularly used by both law enforcement and civilians for hunting, self-defense and sporting applications throughout the United States.
HECKLER & KOCH (“H&K”) is a popular manufacturer of high-quality automatic and semi-automatic hunting, sporting and tactical rifles. Because authentic H&K rifles are relatively expensive and widely sought after, a substantial market for H&K “clones” has developed. An H&K “clone” is a non-H&K manufactured firearm made to look and/or function like a firearm manufactured by H&K. Many H&K rifles and their clones (collectively, “H&K-style rifles”) are chambered for such powerful cartridges as the 5.56 mm×45 NATO (the military equivalent to the 0.223 Remington) and the higher-powered 7.62 mm×51 NATO (the military equivalent to the 0.308 Winchester) rounds. H&K-style rifles also typically use large, heavy bolts that generate significant recoil energy as the bolt travels rearward upon discharge. Accordingly, H&K-style rifles are known throughout the shooting community for having substantially more recoil than other similarly chambered rifles.
Recoil (i.e., “kick”) is the backward momentum generated by a firearm when it is discharged. According to Newton's third law, the recoil generated by discharging a firearm balances the forward momentum of the projectile and exhaust gases expelled during discharge. High-powered cartridges and/or rounds with greater mass produce significantly more recoil energy than low-powered cartridges and/or rounds with less mass. The momentum generated by discharging a shoulder-mounted firearm is transferred to the ground through the body of the shooter and perceived and/or felt by the shooter as recoil.
Perceived recoil is the way in which a shooter perceives the recoil of a firearm. Felt recoil is the amount of recoil actually imparted to a shooter by a discharging firearm. Whereas perceived recoil differs between individuals, the felt recoil generated by a particular firearm is quantifiable and constant.
Perceived and felt recoil negatively impact a shooter's experience and performance by degrading accuracy, creating shooter fatigue, and increasing the time needed for reacquisition of a target between shots. For example, a firearm that is said to “kick like a mule” will be approached by a shooter with trepidation because the perceived recoil is high. Such a shooter will flinch in anticipation of the recoil while firing a shot, which can cause the shooter to jerk rather than smoothly squeeze the trigger. Such a jerking motion will disrupt the shooter's aim. Similarly, a firearm that transfers a large amount of felt recoil to the shooter can reduce the shooter's control over the firearm and make the firearm unpleasant to shoot.
Various mechanisms have been developed to reduce and/or improve felt and perceived recoil. The simplest of these involve the insertion of a lead wedge or other heavy object into one or more cavities in the buttstock of a firearm to increase its overall weight and reduce its momentum during firing. For example, U.S. Patent Application Publication No. 2011/0154707 to Noonan discloses a rifle stock having one or two cylindrical cavities adapted to accept an equal number of similarly sized cylindrical lead bars. While such devices can reduce felt and/or perceived recoil, they add unnecessary weight to the firearm, which can cause a shooter to tire during use. Additionally, these devices often fit the firearm poorly, which can permit the device to dislodge during use and disrupt a shooter's aim, damage the firearm, and/or cause significant injury.
Recoil pads are another type of simple device commonly used to limit recoil. They are typically made of resilient, deformable materials, such as rubber, foam, or leather, and are either attached to the buttstock of a rifle or worn between the buttstock and shoulder of the shooter. Recoil pads reduce perceived and/or felt recoil and prevent slippage of a firearm against a shooter's clothing by providing an additional layer of recoil-absorbing padding between a rifle's buttstock surface and the shooter's shoulder. However, recoil pads do not allow for the use of storage compartments commonly found in many modern synthetic rifle stocks and are not as effective as advanced recoil reducing systems.
Many advanced recoil reducing systems use reciprocating parts such as a hydraulic pistons or recoil spring buffer assemblies to dampen recoil. For example, a recoil spring buffer assembly is a mechanism that attaches to a rifle at the rear of the receiver and comprises a tube containing a spring with a plunger-like device (i.e., a buffer) positioned at the end of the spring nearest the receiver or action. The terms “action” and “receiver” and used interchangeably herein. Upon discharge, the rifle bolt travels rearward from the receiver, contacts the buffer and drives the buffer back into the buffer tube, compressing the buffer spring. The opposing force applied to the bolt by the compressing spring slows the momentum of the bolt, thereby reducing the amount of perceived and/or felt recoil imparted to the shooter. Though effective, these types of devices usually require custom gunsmithing to install, are expensive to manufacture, do not lend themselves to mass production, and are not ordinarily interchangeable between different firearms.
H&K-style rifles are typically manufactured with removable but non-interchangeable buffer assemblies that are notoriously ineffective at reducing the perceived and/or felt recoil of the rifle model for which they are designed. Specifically, the different models of H&K-style rifles are each equipped with differently sized buffers ranging from the small and light G3 standard buffer to the large and strong HK21E machine gun buffer. Because each model of rifle is designed to accept and function with a buffer of a specific size, H&K-style rifle buffers and their existing U.S.-made clones (collectively, “H&K-style buffers”) are not interchangeable between different rifle models. H&K-style rifles are also incompatible with other more effective and modular recoil spring buffer systems such as the buffer assembly used in the AR-15/M16/M4 and AR-10 rifles (collectively, “AR-style rifles”).
AR-style rifles have been used by the U.S. military since the 1960s and are currently one of the more popular style of rifles in the United States. The military success and famous modularity of the AR-style rifle has led to the development of a vast aftermarket for parts and accessories that easily bolt on to existing rifles of various makes. As a result, there are more aftermarket stocks and stock accessories for the AR-15 than any other firearm, including H&K-style rifles. However, AR-style rifle stocks and stock accessories are not compatible with existing H&K-style rifles because AR-style rifle stocks connect to the receiver via the buffer tube component of the rifle's buffer assembly.
Accordingly, there is a need and a demand for a prefabricated, inexpensive and lightweight device that can effectively reduce the amount of perceived and/or felt recoil of an existing H&K-style rifle without the need for custom gunsmithing. There is also a need and desire for a device that can adapt substantially all existing H&K-style rifles to be compatible with the full range of factory and aftermarket AR-style rifle stocks and stock accessories.